This invention relates to oil field tools for use in multiple completion wells, and more particularly, the invention relates to mechanisms for use in conjunction with multiple tubing spiders and slips.
Since the beginning of oil well drilling, tubing of some type has been inserted in the bore of a well to enable it to be produced under control. Some means has always been required for holding the tubing to prevent it moving down the bore further than desired when inserting or "running the string of pipe", piece by piece, or when it was necessary to hold the string of pipe in a given position, Currently in use is a tool known as a spider. A spider is positioned atop a rotary table and aligned with the well bore. Spiders include clamping jaws known as slips. Tubing spiders have been greatly improved over the years, and the spiders of today are power actuated and remotely controlled by compressed air or hydraulically.
Many, if not most, recently drilled oil wells are designed for production from two or more production zones at different depths within a single well bore. Wells having two or more strings for the purpose of producing petroleum products such as oil, gas, distillate, etc., are referred to generally as multiple completion wells, or in the case of two production zones, dual completions. Most wells are dual completion wells having a pair of tubing strings extending from a well head downwardly to the different production zones. The two tubing strings may be of the same diameter, or they may be of different diameters.
As with single completion wells, dual completion wells require some type of holding mechanism for supporting the pipe strings during the running operation. To perform this function, spiders and slips were modified to accommodate two pipe strings rather than one. Spiders adapted for use with dual completion wells contain two slip assemblies, one for each tubing string. For the slip assemblies to properly engage and hold the tubing strings, the tubing strings themselves must be in proper location.
Difficulty has been experienced in the running of pipe strings in multiple completion wells having a diameter which is such that the centers of the tubing strings move off center from the slip centerlines of the spider being used. The tubing strings have been observed to move off their respective centerlines toward the outside of the well bore or toward the center of the well bore, i.e., bow out or bow in. To put the tubing strings into proper alignment so that the slip assemblies can engage the tubing strings, workmen have had to use crowbars to force the tubing into alignment. Obviously, this greatly slows down and complicates the running of tubing strings into a well bore.
It is apparent that a durable, reliable and simple mechanism for maintaining the centerline alignment of the tubing strings in a multiple completion well is highly desirable to permit the rapid and efficient running of pipe strings into a well bore.